Deep water homing device



Oct. 28, 1969 P JR ET AL 3,475,721

DEEP WATER HOMING DEVICE Filed April 30, 1968 7 Sheets-Sheet 1INVENTORS.

X .1 MARVIN CAPPEL J! DAVID R. SUTTON ATTORNEY Oct. 28, 1969 P L, JR" ETAL 3,475,721

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ATTORNEY United States Patent 3,475,721 DEEP WATER HOMIN G DEVICE MarvinCappel, Jr., and David R. Sutton, Jacksonville, Fla, assignors to Mason& Hanger-Silas Mason Co., Inc., Jacksonville, Fla. Continuation-in-partof application Ser. No. 534,357, Mar. 15, 1966. This application Apr.30, 1968, Ser. No. 725,435

Int. Cl. H04b 13/00; G01s 3/80 U.S. Cl. 3406 1 Claim ABSTRACT OF THEDISCLOSURE An underwater direction finding device for response to anaudio generated signal from a distant source, comprising a portablecasing carrying battery energized sonic pick-ups, a first one at theforward end of the casing and three pick-ups rearwardly and laterally ofthe first pick-up and mutually spaced along lines of equal angles lyingin a common plane and radiating in divergent directions from a lineextending from said first pick-up longitudinally of the casing andintersecting the plane of the three rearwardly disposed microphones atright angles, in combination with a sequentiahsimultaneous logic networkadapted for battery operation, including for each sonic pick-up, and insequence, means for amplifying and maintaining the signal to detectionamplitude, means for converting the signal into a pulse, means forfixing the pulse widths, followed in succession for each pick-up bymeans for mixing the plural pulse signals, a resettable time delayswitch providing a continuous signal for a time equal to its delay, andan electronic switch providing an electronic path for the power requiredto operate a signal device carried by the casing.

This invention relates to an underwater direction finding system,primarily intended for use by divers to enable them to readily ascertainthe directional location of an underwater or floating station. Thisapplication is a continuation-in-part of our application filed Mar. 15,1966 Ser. No. 534,357, now abandoned.

Presently used direction finding systems are generally of the binauralor maximum amplitude types, which require a skilled operator and are notadaptable for use by SCUBA (self contained underwater breathingapparatus) equipped divers, who require maximum mobility. This inventionemploys three or more non-directional microphones or pick-ups, asequential-simultaneous logic network, and an on-course indicator suchas a rapidly flashing light or an audible signal, which alleviates theneed for analytical decisions on the part of the user.

The direction finding unit is built using solid state miniaturecomponents and contains a battery power supply. Housing is sealed and ofa material suitable to resist environrnental effects. Both size andweight are a minimum for purposes of maximum utility by the diver.

In use, the diver directs the unit much like a person using aflashlight. When pointed in the direction of the home station, theon-course" signal is activated.

At the station, an audio generator operating in the upper audible orlower ultra-sonic region and transmitting at a single discrete frequencyis employed. Sound generation would be in essentially a sphericaldistribution pattern. No claim is made concerning this generator as itis a commonly used item.

The invention will be described with reference to the accompanyingdrawings, in which:

FIGURE 1 is a schematic view showing the positions of the microphones ofthe direction finder capable of both horizontal and vertical resolution.

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FIGURE 1A is a schematic isometric view showing a further relativepositioning of the microphones of the direction finder and a point Trepresenting an audio generator. Microphone B, C, and D lie in the sameplane and are equidistant from a point 0 in that plane. Lines B0, C0 andDO radiate from the center of the plane .at 120 angles to one another.Microphone A lies on the axial line AO which intersects the plane B CDat right angles.

FIGURE 2 is a schematic view showing the relative positions of themicrophones of the direction finder and the audio generator in plan.

FIGURE 2A is a schematic view showing the relationship of the angle 0 tothe position of the microphones and the audio generator in plan. Theangle 0 is the deviation in degrees of the axial line A0 from theprecise direction of the audio generator Where the line OD is the axisof rotation in plan for such deviation.

FIGURE 3 is a schematic view showing the relative positions of themicrophones of the direction finder and the audio generator in sideelevation.

FIGURE 3A is a schematic view showing the relationship of the angle tothe position of the microphones and the audio generator in sideelevation. The angle 4; is the deviation in degrees of the axial line A0from the precise direction of the audio generator where a line passingthrough the point 0 and parallel to the line BC is the axis of rotationin elevation for such deviation.

FIGURE 4 is a schematic view showing time-phase relationships of pulsesPa, Pb, Pa and Pd generated in response to audio signal reception andplotted as a function of the angular deviation of 0 from the precisedirection of the audio generator for the case where the angle is heldconstantly equal to 0.

FIGURE 5 is a schematic view showing time-phase relationships of pulsesPa, Pb, Po, and Pd generated in response to audio signal reception andplotted as a function of the angular deviation of from the precisedirection of the audio generator for the case where the angle 0 is heldconstantly equal to 0.

FIGURE 6 is a diagrammatic view of a preferred assembly of components ofthe direction finder.

FIGURE 7 is a schematic view depicting the time period relationship ofthe logic level pulses generated by the electronic circuitry in responseto audio signal reception as the direction finder is rotated through 360in plan while the angle is held constant at 0 (i.e., about the line DO"as axis of rotation).

FIGURE 8 is a schematic view depicting the time period relationship ofthe logic level pulses generated by the electronic circuitry in responseto audio signal reception as the direction finder is rotated through 360in elevation while the angle 0 is held constant at 0 (i.e., about a linethrough the point 0 parallel to the line BC as axis of rotation).

FIGURE 9 is an artists conception of a suitable direction finder encasedfor use underwater with the positions of the microphones shown thereon.

FIGURE 10 is a front view artists conception of a suitable directionfinder encased for use underwater with the positions of the microphonesshown thereon.

FIGURE 11 is a schematic isometric view showing the relative positionsof the microphones of the direction finder and a point T andillustrating the cone of critical resolution.

Four audio pick-ups or microphones are arranged in a generalconfiguration as depicted in FIGURES 1 and 1A for a direction finderwhich is capable of resolving the direction to an audio generatorregardless of its location providing it is within range of the radiatedsonic signal.

Referring to FIGURE 1A, consider that a sonic signal of X Wave-length(in sea water) is generated at Point T. In order for the directionfinder to give an oncourse signal, it must be physically directed towardthis point T. In this attitude, the positive phase of one generatedcycle will first be received by microphone A which, as will be discussedlater, generates an enabling signal on pulse, Pa. Within the time ofthis pulse width, the signal must be received by microphones B, C, and Dand the relative times of reception at B, C, and D must be essentiallycoincident.

Because the critical angle in plan, or the maximum angular deviationfrom the precise direction of the base station which the directionfinder may be directed and still produce or display an on-course signal(shown as angle in FIG. 2B), is a function of the relative physicalposition of the microphones B and C (dimension Y in FIG. 2A), thewave-length of the homing signal, and the pulse width generated by theelectronic circuitry associated with each microphone; the degree ofresolution is fixed by the choice of these parameters. To illustrate theeffect of various choices upon resolution, consider FIGURE 4. Here thepulses Pa, Pb, Fe, and Pd generated in response to homing signalreception at points A, B, C and D are plotted as a function of angulardeviation 0, from the precise direction of point T. For thisconsideration, the angle is held constant at 0. Dimension X of FIG. 2Ais 0.3x and the pulse width generated by the electronic circuitryassociated with microphone circuit A (Pa) is 0.4).. The pulse widthsgenerated by the electronic circuitry associated with microphonecircuits B (Pb), C (P0), and D (Pd) are 0:07) (For purpose of clarity,units of time are related to equivalent units of wave-length.) Twoseries of curves are shown, one with the dimension Y equal to 0.1x andthe other with Y equal to 0.4).. The critical angle, 0c, is the angle atwhich Pb and Pc become non-coincident. Since 00 is related to thedimension Y it can be seen in FIG. 4 that the critical angle isapproximately *-20 degrees and 5 degrees respectively for the two valuesof Y illustrated.

FIG. 7 depicts the time period relationship of the logic level pulsesgenerated by the microphone circuits as the direction finder is rotatedthrough 360 in plan with respect to the audio generator for the sameconditions as FIGURE 4, except that only one choice of dimension Y isillustrated, namely Y=O.l'y.

The critical angle 00 is also related to the pulse widths Pb and P0(these should be nearly equal for an optimum design), and variousdegrees of resolution are similarly dictated by choice of these pulsewidths. The critical angle 6c decreases for decreasing pulse widths.

Similarly the critical angle in elevation (shown as angle in FIG. 3B) isa function of the relative physical position of the microphones B, C andD (see FIG. 3A), the wave-length of the homing signal, and the pulsewidth generated by the electronic circuitry associated with eachmicrophone; and the degree of resolution is fixed by the choice of theseparameters. FIGURE 5 illustrates the effect of various choices similarlyto FIGURE 4. Here the pulses Pa, Pb, P0 and Pd generated in response tohoming signal reception at points A, B," C, and D are plotted as afunction of angular deviation from the precise direction of point T.FIGURE 5 is plotted for the case where 0 is held constant at 0 and thuspulses Pb and Pr: are shown coincident. Dimension X of FIG. 3A is 0.3).,and the pulse width generated by the electronic circuitry associatedwith microphone circuit A (Pa) is 0.4%. The pulse width generated by theelectronic circuitry associated with microphone circuits B (Pb), C (P0),and D (Pd) are 0.07).. (For purpose of clarity, units of time arerelated to equivalent units of wavelength.) Two series of curves areshown, one with the dimension Y equal to 0.1'y and the other with Yequal to O.47\.

The critical angle, c, is the angle at which Pb, Pc and Pd becomenon-coincident. Since c is related to the dimension Y it can be seen inFIG. 5 that the critical angle is approximately :24 degrees and :6degrees respectively for the two values of Y illustrated.

FIG. 8 depicts the time period relationship of the logic level pulsesgenerated by the microphone circuits as the direction finder is rotatedthrough 360 in elevation with respect to the audio generator for thesame conditions as FIGURE 5 except that only one choice of dimension Yis illustrated, namely Y=O.l

The critical angle c is also related to the pulse widths Pb, Pc and Pdand choice of these pulse widths will effect the degree of resolutionsuch that the critical angle will decrease for decreasing pulse widths.

From the above, it is obvious that the direction finder can be built sothat the critical angles are selected single values or it can be builtin such a manner that the critical angles can be adjusted by the user,allowing him to first use comparatively large angles for initialorientation and then smaller angles for more precise bearing.

FIG. 6 is a block diagram of a preferred embodiment of the directionfinding unit. Depicted are the components of the unit and theirrespective arrangement. To one versed in the state of the art, it isobvious that specific circuit components and arrangement are a matter ofdesigners choice and many combinations can give equally satisfactoryresults.

The Threshold Circuit is, in effect, an automatic gain control. Itmaintains the signal at a suitable amplitude for proper detection, andat the same time, rejects unwanted background signals or noise by virtueof its amplitude discrimination.

The Pulse Former converts the sine wave signal transmitted from themicrophone through the intermediary circuits (upon reception of a sonicsignal) into a pulse by electronic switch action. The circuit may besimilar to the familiar Sch-mitt trigger, but is not limited to this.The leading edge of the pulse thus formed triggers the followingone-shot circuit (monostable multivibrators) which fixes the final pulsewidths of Pa, Pb, P0, and Pd as shown in FIGURES 4, 5, 7, and 8.

The amplifiers used throughout the circuit maintain a suitable signallevel, this being standard practice.

The resettable delay is a well known electronic time delay switch. Onreception of a pulse type signal, it closes and provides a continuoussignal to the Lamp Driver for a period of time equal to its designeddelay. For this application, this time will be greater than one cycle ofthe transmitted sonic signal, but less than two cycles. :If, during theperiod of its delay time, the resettable delay receives another pulsesignal, its timing mechanism will be reset and it will begin timing anewfrom that instant and the circuit will remain closed. Failure to receivea following pulse during the period of its delay time will result in thecircuit opening until such time as further pulses are received at itsinput. Thus, receipt of one pulse each cycle is sufiicient to cause theresettable delay to hold the lamp driver on. The lamp driver is anelectronic switch or gate. While receiving a closed signal from theresettable delay, it provides an electrical path for power suitable tooperate the oncourse signal lamp. The AND circuit and logic levelamplifier are common logic function circuits which those skilled in thedesign of logic circuits and solid state electronics are familiar with.

FIGURE 9 is a concept of the direction finder package. Size and shapeapproximates that of a standard two cell flashlight, with the additionof the mounts for microphones B, C, and D. The ring at the rear is forattaching to a belt snap. Microphone A is mounted in the nose cone andthe on-course light in the cylinder wall. The unit is completely selfcontained. Many variations in the package are possible.

In principle, this same basic arrangement could be adapted for use inair rather than a water medium with any suitable packaging of the devicebeing practical.

Referring to FIGURE 6 of the drawings, it will be seen that eachmicrophone (termed the Sonic Pick-Up) feeds to its indicated band-passfilter which latter is shown related to the sonic signal by fc: V/)\,where V is the signal velocity in the medium of transmission. Thefiltered wave is then fed to the indicated amplifier, to the ThresholdCircuit, to the Pulse Former, to the One Shot and, as indicated at theOne Shot, outwardly as pulse Pa, Pb, P0 or Pd, as the case may be.

The four pulse outputs are mixed, in the manner shown. Pulse outputs Pa,Pb, P0 and Pd are fed to and jointly mixed by a common Logic Level ANDCircuit, followed by the action of a Logic Level Amplifier. The outputof the Logic Level Amplifier is led by the Resettable Delay to a LampDriver.

The logic principle upon which the homing device is based is that thepulse Pa must be received before either Pb, Pc, or Pd and that thepulses Pb, Pc or Pd must be received essentially coincident in order toinitiate the oncourse signal. That is the principle demonstrated in FIG-URES 4, 5, 7 and 8. This explains the reason for the particular methodof pulse mixing. The true logic level signal (R) at the input to theresettable delay in FIG- URE 6 is:

R=PaPbPcPd Thus, the function R can only be true if Pa, Pb, Po and Pdare coincident during some portion of their pulse widths.

The circuit now shown in FIGURE 6 is the preferred embodiment for thisinvention and is possible because of the choice of parameters (x, y, Pa,Pb, Pc, Pd). This circuit forms directly the desired function:

R=PaPbPcPd Referring to FIGURE 11, the cone of critical resolution isillustrated. This cone is formed with-its apex at O by rotating themicrophone A in a motion similar to a precession such that theboundaries of this cone define the degree of resolution of the directionto point T as determined by the direction finder. This cone is somewhateliptical in cross section for the choice of parameters given in FIGURES4 and 5, and is fixed only by the choice of parameters mentioned inrelation to these figures. The cone may be thought of as describing atype of solid critical angle.

It will be understood that the casing shown in FIG- URE 9 will beprovided with a manual switch arrangement for breaking the circuit fromthe source of power, and inasmuch as this is a common and wellunderstood arrangement, particularly with respect to dry cell flashlightcasings, it has not been illustrated in the drawings.

It should be understood that the direction finder as herein beforedescribed may be made to operate with fewer than the four microphonesillustrated and described but its usefulness will be limited to a muchlarger cone of critical resolution.

Having described my invention, what I claim and desire to secure byLetters Patent is as follows:

1. A homing device adapted for response to a distant audio generatedsignal, comprising a portable casing, a plurality of sonic pickups inexcess of three operatively associated with said casing including afirst sonic pickup disposed forwardly of the others, said others beingdisposed rearwardly and angularly of said first pickup, and an on-courseindicator, a sequential-simultaneous logic network adapted for batteryoperation including for each sonic pickup, and in sequence, means foramplifying and maintaining the signal to detection amplitude, means forconverting the signal into a pulse by electronic switch action, andmeans for fixing the pulse widths, followed, in succession for eachsonic pickup by means for mixing the plural pulse signals, a resettabletime delay switch adapted to provide a continuous signal for a period oftime equal to its delay, a signal device, and an electronic switchproviding an electrical path for power required to operate said signaldevice, in which the casing carries the first sonic pickup at itsforward end and carries three sonic pickups rearwardly and laterallythereof and mutually spaced along lines of equal angles lying in a comonplane and radiating in divergent directions from a line extending fromsaid first sonic pickup longitudinally of the casing and intersectingthe plane of the three rearwardly disposed microphones at right angles.

References Cited UNITED STATES PATENTS 2,721,315 10/1955 Snyder 3406RICHARD A. FARLEY, Primary Examiner U.S. Cl. X.R.

